Recently, fuel cells are known in which fuel gas or fuel fluid containing a large amount of hydrogen or the like and oxygen (air) as oxidizing gas are fed and electrochemically reacted to generate electric power. Examples include a fuel cell having a structure such that a proton conductor membrane as an electrolyte membrane is sandwiched between a fuel electrode and an air electrode.
Fuel cells can be mounted as power sources on vehicles, such as automobiles, and they are expected to be applied to electric cars or hybrid cars. In addition, the fuel cells have a structure which can be easily reduced in weight or size, and hence an attempt is made to apply the fuel cells to power sources for various information processing apparatuses, such as notebook personal computers, portable phones, and personal digital assistants (PDA). Further, electric power generated by household or personal fuel cells is supplied to electric appliances, such as so-called information appliances.
By the way, the above-mentioned fuel cell generates desired electric power by feeding hydrogen or methanol used as a fuel and oxygen in a satisfactory amount. Therefore, in the fuel cell, for steadily supplying electric power to a loading apparatus which utilizes the electric power generated, it is necessary to steadily feed the fuel to the fuel cell depending on the load. Especially in a so-called direct methanol fuel cell, it is desired to optimize the feed rate of the fuel.
The power generating system using a conventional fuel cell, however, has no means for obtaining the load information about a loading apparatus, e.g., a portable compact disc player or a portable phone.
There are power generating systems using a fuel cell and having a construction such that a plurality of loading apparatus are connected to the system and the individual loading apparatus need different voltages and electric currents. In the systems of this type, it is necessary to determine the optimum electric power to be generated depending on the load conditions and to finely control the feed rate of the fuel.
Further, there are power generating systems using a fuel cell and having connected thereto a loading apparatus that changes the state of power consumption, for example, a loading apparatus that requires predetermined electric power in a normal state and needs only a small amount of electric power in, e.g., a sleep mode. In such a case, in the systems of this type, ideally, an output voltage or the like can be arbitrarily controlled, but there are no means for obtaining the information from the loading apparatus and hence such control cannot be achieved.
In view of the above problems, the present invention has been achieved, and a task is to provide a fuel cell power generating system, a method for controlling fuel cell power generation, and a fuel cell power generating apparatus, which are advantageous not only in that steady power supply can be achieved according to the load, but also in that the power supply can be flexibly controlled even when different types of loading apparatus utilize the electric power generated.